Search

A study was made on the molecular and structural changes occurring in the protein and starch components of sorghum flour when fermented to prepare typical non-malted Sudanese foods. Protein solubility and SDS-PAGE studies indicated that water-soluble proteins are the main target of hydrolysis during fermentation. Proteolysis products are taken up for bacterial growth. Kafirins are among the proteins left intact by proteolytic events in the fermentation step. Upon cooking in boiling water kafirins are converted into protein aggregates almost insoluble even in the presence of 8 M urea and of disulphide-reducing agents. Viscoamylographic and microstructural studies indicate that fermentation leads to the release of starch granules from very compact structures in the original sorghum flour, in which proteolysis-sensitive, water-soluble proteins form an essential part of the outermost shell of large structures, where starch granules are embedded into a kafirin-rich protein matrix that is not affected by proteolytic events during fermentation. [ABSTRACT FROM AUTHOR]

The influence of egg pasteurisation and of thermal treatment(s) of fresh egg pasta on the protein network in the pasta were studied. Protein structural parameters were correlated with the physico-chemical and rheological characteristics of pasta. Twelve samples of fresh egg pasta were laboratory-produced, using raw or pasteurised whole egg, and either left untreated or submitted to one or two pasteurisation processes. Industrial pasteurisation of the eggs did not affect the protein network of pasta or its rheological and functional characteristics. Double thermal pasteurisation of egg pasta deeply influenced its structural characteristics, due to the formation of a tight protein network stabilised by disulfide bonds, in which ovalbumin plays an essential role. This tight protein network affected the cooking behaviour and the rheological properties of fresh egg pasta, decreasing weight increase upon cooking and break strain, while increasing break load and Young modulus. The indexes derived from these studies were applied to the characterisation of 24 commercial samples of fresh egg pasta. By using the Young modulus before and after cooking (rheological parameters) and protein solubility in buffer-saline (structural parameter), it was possible to discriminate three groups of samples as a function of the severity of their thermal treatment. [ABSTRACT FROM AUTHOR]